Hello kid,
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If you forgot your registration ID then Checkout your mail box for it or message box because while the time of registration you could've received it via msge or mail.
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Now, if you gave your mail for OTP and didn't received it, do check the entered mail whether it's correct or not spelling by spelling and if correct delete few messages and keep refreshing. Now do try for OTP after this process is completed. You will surely get it.
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here what happens it's when the mail is loaded with mails it takes time for new mail arrive so if you delete few mails it becomes easy for new mails